14C-DMT accumulates in rat brain cortical slices incubated at 37 C. This process has many of the properties of an active uptake mechanism. It is temperature-sensitive, sodium-dependent, saturable, and is inhibited by metabolic inhibitors. Tryptamine derivatives were more effective than the catecholamines in competing for 14C-DMT accumulation. A number of psychotropic drugs were inhibitors of 14C-DMT accumulation. In general, irrespective of pharmacologic class, the tertiary amines were more potent than the secondary or primary amines, although there were some exceptions. Most of the accumulated 14C-DMT was associated with the cytoplasmic fraction. Of the portion associated with the crude mitochondrial fraction, 54.4% was associated with nerve-ending fraction.